Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $57.92   7.605%   $62.3248   $62.32   $62.30   $62.30  
  Purchase #2 $245.88   9.552%   $269.3665   $269.37   $269.35   $269.40  
  Purchase #3 $73.74   3.480%   $76.3062   $76.31   $76.30   $76.30  
  Purchase #4 $156.37   11.224%   $173.921   $173.92   $173.90   $173.90  
  Purchase #5 $113.91   5.180%   $119.8105   $119.81   $119.80   $119.80  
  Purchase #6 $195.94   8.403%   $212.4048   $212.40   $212.40   $212.40  
  Purchase #7 $79.66   10.285%   $87.853   $87.85   $87.85   $87.90  
  7 purchase totals = $923.42       $1,001.9868   $1,001.98   $1,001.90   $1,002.00